Modeling pressure effects on the turbulent burning velocity for lean hydrogen/air premixed combustion

Abstract

We investigate and model pressure effects on the turbulent burning velocity over a range of pressures and turbulence intensities with the direct numerical simulation (DNS) of statistically planar turbulent premixed flames for lean hydrogen/air mixture. DNS results indicate that the stretch factor has an impact on the turbulent burning velocity and flame surface area at elevated pressures. In particular, the enhanced stretch factor at high pressures increases the ratio of turbulent and laminar burning velocities, diminishing the “bending” effect. Based on a good consistency between turbulent and laminar burning velocities with respect to flame stretch, a lookup table formed by laminar flame data is employed to model the stretch factor in turbulent flames at various pressures. A predictive model for the turbulent burning velocity is then developed by combining sub models of the stretch factor and flame surface area. The overall good agreement between model predictions and DNS results demonstrates that the proposed model is able to quantitatively predict the turbulent burning velocity over a range of pressures and turbulence intensities in homogeneous isotropic turbulence.